use base64::prelude::*;

const KD: [u16;16] = [
    0x44D7,0x26BC,0x626B,0x135E,0x5789,0x35E2,0x7135,0x09AF,
    0x4D78,0x2F13,0x6BC4,0x1AF1,0x5E26,0x3C4D,0x789A,0x47AC,
];

const S0: [u8;256] = [
    0x3e,0x72,0x5b,0x47,0xca,0xe0,0x00,0x33,0x04,0xd1,0x54,0x98,0x09,0xb9,0x6d,0xcb,
    0x7b,0x1b,0xf9,0x32,0xaf,0x9d,0x6a,0xa5,0xb8,0x2d,0xfc,0x1d,0x08,0x53,0x03,0x90,
    0x4d,0x4e,0x84,0x99,0xe4,0xce,0xd9,0x91,0xdd,0xb6,0x85,0x48,0x8b,0x29,0x6e,0xac,
    0xcd,0xc1,0xf8,0x1e,0x73,0x43,0x69,0xc6,0xb5,0xbd,0xfd,0x39,0x63,0x20,0xd4,0x38,
    0x76,0x7d,0xb2,0xa7,0xcf,0xed,0x57,0xc5,0xf3,0x2c,0xbb,0x14,0x21,0x06,0x55,0x9b,
    0xe3,0xef,0x5e,0x31,0x4f,0x7f,0x5a,0xa4,0x0d,0x82,0x51,0x49,0x5f,0xba,0x58,0x1c,
    0x4a,0x16,0xd5,0x17,0xa8,0x92,0x24,0x1f,0x8c,0xff,0xd8,0xae,0x2e,0x01,0xd3,0xad,
    0x3b,0x4b,0xda,0x46,0xeb,0xc9,0xde,0x9a,0x8f,0x87,0xd7,0x3a,0x80,0x6f,0x2f,0xc8,
    0xb1,0xb4,0x37,0xf7,0x0a,0x22,0x13,0x28,0x7c,0xcc,0x3c,0x89,0xc7,0xc3,0x96,0x56,
    0x07,0xbf,0x7e,0xf0,0x0b,0x2b,0x97,0x52,0x35,0x41,0x79,0x61,0xa6,0x4c,0x10,0xfe,
    0xbc,0x26,0x95,0x88,0x8a,0xb0,0xa3,0xfb,0xc0,0x18,0x94,0xf2,0xe1,0xe5,0xe9,0x5d,
    0xd0,0xdc,0x11,0x66,0x64,0x5c,0xec,0x59,0x42,0x75,0x12,0xf5,0x74,0x9c,0xaa,0x23,
    0x0e,0x86,0xab,0xbe,0x2a,0x02,0xe7,0x67,0xe6,0x44,0xa2,0x6c,0xc2,0x93,0x9f,0xf1,
    0xf6,0xfa,0x36,0xd2,0x50,0x68,0x9e,0x62,0x71,0x15,0x3d,0xd6,0x40,0xc4,0xe2,0x0f,
    0x8e,0x83,0x77,0x6b,0x25,0x05,0x3f,0x0c,0x30,0xea,0x70,0xb7,0xa1,0xe8,0xa9,0x65,
    0x8d,0x27,0x1a,0xdb,0x81,0xb3,0xa0,0xf4,0x45,0x7a,0x19,0xdf,0xee,0x78,0x34,0x60,
];

const S1: [u8;256] = [
    0x55,0xc2,0x63,0x71,0x3b,0xc8,0x47,0x86,0x9f,0x3c,0xda,0x5b,0x29,0xaa,0xfd,0x77,
    0x8c,0xc5,0x94,0x0c,0xa6,0x1a,0x13,0x00,0xe3,0xa8,0x16,0x72,0x40,0xf9,0xf8,0x42,
    0x44,0x26,0x68,0x96,0x81,0xd9,0x45,0x3e,0x10,0x76,0xc6,0xa7,0x8b,0x39,0x43,0xe1,
    0x3a,0xb5,0x56,0x2a,0xc0,0x6d,0xb3,0x05,0x22,0x66,0xbf,0xdc,0x0b,0xfa,0x62,0x48,
    0xdd,0x20,0x11,0x06,0x36,0xc9,0xc1,0xcf,0xf6,0x27,0x52,0xbb,0x69,0xf5,0xd4,0x87,
    0x7f,0x84,0x4c,0xd2,0x9c,0x57,0xa4,0xbc,0x4f,0x9a,0xdf,0xfe,0xd6,0x8d,0x7a,0xeb,
    0x2b,0x53,0xd8,0x5c,0xa1,0x14,0x17,0xfb,0x23,0xd5,0x7d,0x30,0x67,0x73,0x08,0x09,
    0xee,0xb7,0x70,0x3f,0x61,0xb2,0x19,0x8e,0x4e,0xe5,0x4b,0x93,0x8f,0x5d,0xdb,0xa9,
    0xad,0xf1,0xae,0x2e,0xcb,0x0d,0xfc,0xf4,0x2d,0x46,0x6e,0x1d,0x97,0xe8,0xd1,0xe9,
    0x4d,0x37,0xa5,0x75,0x5e,0x83,0x9e,0xab,0x82,0x9d,0xb9,0x1c,0xe0,0xcd,0x49,0x89,
    0x01,0xb6,0xbd,0x58,0x24,0xa2,0x5f,0x38,0x78,0x99,0x15,0x90,0x50,0xb8,0x95,0xe4,
    0xd0,0x91,0xc7,0xce,0xed,0x0f,0xb4,0x6f,0xa0,0xcc,0xf0,0x02,0x4a,0x79,0xc3,0xde,
    0xa3,0xef,0xea,0x51,0xe6,0x6b,0x18,0xec,0x1b,0x2c,0x80,0xf7,0x74,0xe7,0xff,0x21,
    0x5a,0x6a,0x54,0x1e,0x41,0x31,0x92,0x35,0xc4,0x33,0x07,0x0a,0xba,0x7e,0x0e,0x34,
    0x88,0xb1,0x98,0x7c,0xf3,0x3d,0x60,0x6c,0x7b,0xca,0xd3,0x1f,0x32,0x65,0x04,0x28,
    0x64,0xbe,0x85,0x9b,0x2f,0x59,0x8a,0xd7,0xb0,0x25,0xac,0xaf,0x12,0x03,0xe2,0xf2,

];

// wrap the overflow
fn add_m(a: u32, b: u32) -> u32 {
    let c = a.wrapping_add(b);
    (c & 0x7FFFFFFF).wrapping_add(c >> 31)
}

fn rot(a: u32, k: u32) -> u32 {
    (a << k) | (a >> (32 - k))
}


const LFSR_SIZE: usize = 16;
const BRC_SIZE: usize = 4;

struct ZUC {
    lfsr_s: [u32; LFSR_SIZE],
    f_r1: u32,
    f_r2: u32,
    brc_x: [u32; BRC_SIZE],
}

impl ZUC {
    fn new() -> Self {
        ZUC {
            lfsr_s: [0; LFSR_SIZE],
            f_r1: 0,
            f_r2: 0,
            brc_x: [0; BRC_SIZE],
        }
    }

    fn mul_by_pow2(x: u32, k: u32) -> u32 {
        ((x << k) | (x >> (31 - k))) & 0x7FFFFFFF
    }

    fn lfsr_with_initialization_mode(&mut self, u: u32) {
        let mut f = self.lfsr_s[0];
        let mut v = Self::mul_by_pow2(self.lfsr_s[0], 8);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[4], 20);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[10], 21);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[13], 17);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[15], 15);
        f = add_m(f, v);

        f = add_m(f, u);

        for i in 0..15 {
            self.lfsr_s[i] = self.lfsr_s[i + 1];
        }
        self.lfsr_s[15] = f;
    }

    fn lfsr_with_work_mode(&mut self) {
        let mut f = self.lfsr_s[0];
        let mut v = Self::mul_by_pow2(self.lfsr_s[0], 8);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[4], 20);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[10], 21);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[13], 17);
        f = add_m(f, v);

        v = Self::mul_by_pow2(self.lfsr_s[15], 15);
        f = add_m(f, v);

        for i in 0..15 {
            self.lfsr_s[i] = self.lfsr_s[i + 1];
        }
        self.lfsr_s[15] = f;
    }

    fn bit_reorganization(&mut self) {
        self.brc_x[0] = ((self.lfsr_s[15] & 0x7FFF8000) << 1) | (self.lfsr_s[14] & 0xFFFF);
        self.brc_x[1] = ((self.lfsr_s[11] & 0xFFFF) << 16) | (self.lfsr_s[9] >> 15);
        self.brc_x[2] = ((self.lfsr_s[7] & 0xFFFF) << 16) | (self.lfsr_s[5] >> 15);
        self.brc_x[3] = ((self.lfsr_s[2] & 0xFFFF) << 16) | (self.lfsr_s[0] >> 15);
    }

    fn l1(x: u32) -> u32 {
        x ^ rot(x, 2) ^ rot(x, 10) ^ rot(x, 18) ^ rot(x, 24)
    }

    fn l2(x: u32) -> u32 {
        x ^ rot(x, 8) ^ rot(x, 14) ^ rot(x, 22) ^ rot(x, 30)
    }

    fn make_u32(a: u8, b: u8, c: u8, d: u8) -> u32 {
        ((a as u32) << 24) | ((b as u32) << 16) | ((c as u32) << 8) | (d as u32)
    }

    fn f(&mut self) -> u32 {
        let w = (self.brc_x[0] ^ self.f_r1).wrapping_add(self.f_r2);
        let w1 = self.f_r1.wrapping_add(self.brc_x[1]);
        let w2 = self.f_r2 ^ self.brc_x[2];
        let u = Self::l1((w1 << 16) | (w2 >> 16));
        let v = Self::l2((w2 << 16) | (w1 >> 16));
        self.f_r1 = Self::make_u32(S0[(u >> 24) as usize], S1[((u >> 16) & 0xFF) as usize], S0[((u >> 8) & 0xFF) as usize], S1[(u & 0xFF) as usize]);
        self.f_r2 = Self::make_u32(S0[(v >> 24) as usize], S1[((v >> 16) & 0xFF) as usize], S0[((v >> 8) & 0xFF) as usize], S1[(v & 0xFF) as usize]);

        w
    }

    fn initialization(&mut self, k: &[u8], iv: &[u8]) {
        for i in 0..16 {
            self.lfsr_s[i] = ((k[i] as u32) << 23) | ((KD[i] as u32) << 8) | (iv[i] as u32);
        }
        self.f_r1 = 0;
        self.f_r2 = 0;
        for _ in 0..32 {
            self.bit_reorganization();
            let w = self.f();
            self.lfsr_with_initialization_mode(w >> 1);
        }

        self.bit_reorganization();
        self.f();
        self.lfsr_with_work_mode();
    }

    fn generate_key_stream(&mut self, len: usize) -> Vec<u32> {
        let mut key_stream: Vec<u32> = vec![0u32; len];
        for i in 0..len {
            self.bit_reorganization();
            key_stream[i] = self.f() ^ self.brc_x[3];
            self.lfsr_with_work_mode();
        }
        key_stream
    }
}

fn pkcs7(input: String) -> Vec<u8> {
    let mut input = input.as_bytes().to_vec();
    let len = input.len();
    let pad = 4 - len % 4;
    for _ in 0..pad {
        input.push(pad as u8);
    }
    return input;
}

pub fn encryption(input: String) -> String {
    let key = [0u8; 16];
    let iv = [1u8; 16];
    let input = pkcs7(input);
    let len = input.len();
    let mut zuc = ZUC::new();
    zuc.initialization(&key, &iv);
    let key_stream = zuc.generate_key_stream(len / 4);
    let mut result = vec![0u8; len];
    for i in 0..len {
        result[i] = input[i] ^ (key_stream[i / 4] >> (8 * (3 - i % 4))) as u8;
    }
    BASE64_STANDARD.encode(&result)
}
